net/9p/trans_virtio.c

   1 /*
   2  * The Virtio 9p transport driver
   3  *
   4  * This is a block based transport driver based on the lguest block driver
   5  * code.
   6  *
   7  *  Copyright (C) 2007, 2008 Eric Van Hensbergen, IBM Corporation
   8  *
   9  *  Based on virtio console driver
  10  *  Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
  11  *
  12  *  This program is free software; you can redistribute it and/or modify
  13  *  it under the terms of the GNU General Public License version 2
  14  *  as published by the Free Software Foundation.
  15  *
  16  *  This program is distributed in the hope that it will be useful,
  17  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  *  GNU General Public License for more details.
  20  *
  21  *  You should have received a copy of the GNU General Public License
  22  *  along with this program; if not, write to:
  23  *  Free Software Foundation
  24  *  51 Franklin Street, Fifth Floor
  25  *  Boston, MA  02111-1301  USA
  26  *
  27  */
  28
  29 #include <linux/in.h>
  30 #include <linux/module.h>
  31 #include <linux/net.h>
  32 #include <linux/ipv6.h>
  33 #include <linux/errno.h>
  34 #include <linux/kernel.h>
  35 #include <linux/un.h>
  36 #include <linux/uaccess.h>
  37 #include <linux/inet.h>
  38 #include <linux/idr.h>
  39 #include <linux/file.h>
  40 #include <net/9p/9p.h>
  41 #include <linux/parser.h>
  42 #include <net/9p/client.h>
  43 #include <net/9p/transport.h>
  44 #include <linux/scatterlist.h>
  45 #include <linux/virtio.h>
  46 #include <linux/virtio_9p.h>
  47
  48 #define VIRTQUEUE_NUM   128
  49
  50 /* a single mutex to manage channel initialization and attachment */
  51 static DEFINE_MUTEX(virtio_9p_lock);
  52 /* global which tracks highest initialized channel */
  53 static int chan_index;
  54
  55 /**
  56  * struct virtio_chan - per-instance transport information
  57  * @initialized: whether the channel is initialized
  58  * @inuse: whether the channel is in use
  59  * @lock: protects multiple elements within this structure
  60  * @vdev: virtio dev associated with this channel
  61  * @vq: virtio queue associated with this channel
  62  * @tagpool: accounting for tag ids (and request slots)
  63  * @reqs: array of request slots
  64  * @max_tag: current number of request_slots allocated
  65  * @sg: scatter gather list which is used to pack a request (protected?)
  66  *
  67  * We keep all per-channel information in a structure.
  68  * This structure is allocated within the devices dev->mem space.
  69  * A pointer to the structure will get put in the transport private.
  70  *
  71  */
  72
  73 static struct virtio_chan {
  74         bool initialized;
  75         bool inuse;
  76
  77         spinlock_t lock;
  78
  79         struct p9_client *client;
  80         struct virtio_device *vdev;
  81         struct virtqueue *vq;
  82
  83         /* Scatterlist: can be too big for stack. */
  84         struct scatterlist sg[VIRTQUEUE_NUM];
  85 } channels[MAX_9P_CHAN];
  86
  87 /* How many bytes left in this page. */
  88 static unsigned int rest_of_page(void *data)
  89 {
  90         return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE);
  91 }
  92
  93 /**
  94  * p9_virtio_close - reclaim resources of a channel
  95  * @trans: transport state
  96  *
  97  * This reclaims a channel by freeing its resources and
  98  * reseting its inuse flag.
  99  *
 100  */
 101
 102 static void p9_virtio_close(struct p9_client *client)
 103 {
 104         struct virtio_chan *chan = client->trans;
 105
 106         mutex_lock(&virtio_9p_lock);
 107         chan->inuse = false;
 108         mutex_unlock(&virtio_9p_lock);
 109 }
 110
 111 /**
 112  * req_done - callback which signals activity from the server
 113  * @vq: virtio queue activity was received on
 114  *
 115  * This notifies us that the server has triggered some activity
 116  * on the virtio channel - most likely a response to request we
 117  * sent.  Figure out which requests now have responses and wake up
 118  * those threads.
 119  *
 120  * Bugs: could do with some additional sanity checking, but appears to work.
 121  *
 122  */
 123
 124 static void req_done(struct virtqueue *vq)
 125 {
 126         struct virtio_chan *chan = vq->vdev->priv;
 127         struct p9_fcall *rc;
 128         unsigned int len;
 129         struct p9_req_t *req;
 130
 131         P9_DPRINTK(P9_DEBUG_TRANS, ": request done\n");
 132
 133         while ((rc = chan->vq->vq_ops->get_buf(chan->vq, &len)) != NULL) {
 134                 P9_DPRINTK(P9_DEBUG_TRANS, ": rc %p\n", rc);
 135                 P9_DPRINTK(P9_DEBUG_TRANS, ": lookup tag %d\n", rc->tag);
 136                 req = p9_tag_lookup(chan->client, rc->tag);
 137                 req->status = REQ_STATUS_RCVD;
 138                 p9_client_cb(chan->client, req);
 139         }
 140 }
 141
 142 /**
 143  * pack_sg_list - pack a scatter gather list from a linear buffer
 144  * @sg: scatter/gather list to pack into
 145  * @start: which segment of the sg_list to start at
 146  * @limit: maximum segment to pack data to
 147  * @data: data to pack into scatter/gather list
 148  * @count: amount of data to pack into the scatter/gather list
 149  *
 150  * sg_lists have multiple segments of various sizes.  This will pack
 151  * arbitrary data into an existing scatter gather list, segmenting the
 152  * data as necessary within constraints.
 153  *
 154  */
 155
 156 static int
 157 pack_sg_list(struct scatterlist *sg, int start, int limit, char *data,
 158                                                                 int count)
 159 {
 160         int s;
 161         int index = start;
 162
 163         while (count) {
 164                 s = rest_of_page(data);
 165                 if (s > count)
 166                         s = count;
 167                 sg_set_buf(&sg[index++], data, s);
 168                 count -= s;
 169                 data += s;
 170                 BUG_ON(index > limit);
 171         }
 172
 173         return index-start;
 174 }
 175
 176 /* We don't currently allow canceling of virtio requests */
 177 static int p9_virtio_cancel(struct p9_client *client, struct p9_req_t *req)
 178 {
 179         return 1;
 180 }
 181
 182 /**
 183  * p9_virtio_request - issue a request
 184  * @t: transport state
 185  * @tc: &p9_fcall request to transmit
 186  * @rc: &p9_fcall to put reponse into
 187  *
 188  */
 189
 190 static int
 191 p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
 192 {
 193         int in, out;
 194         struct virtio_chan *chan = client->trans;
 195         char *rdata = (char *)req->rc+sizeof(struct p9_fcall);
 196
 197         P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request\n");
 198
 199         out = pack_sg_list(chan->sg, 0, VIRTQUEUE_NUM, req->tc->sdata,
 200                                                                 req->tc->size);
 201         in = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM-out, rdata,
 202                                                                 client->msize);
 203
 204         req->status = REQ_STATUS_SENT;
 205
 206         if (chan->vq->vq_ops->add_buf(chan->vq, chan->sg, out, in, req->tc)) {
 207                 P9_DPRINTK(P9_DEBUG_TRANS,
 208                         "9p debug: virtio rpc add_buf returned failure");
 209                 return -EIO;
 210         }
 211
 212         chan->vq->vq_ops->kick(chan->vq);
 213
 214         P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request kicked\n");
 215         return 0;
 216 }
 217
 218 /**
 219  * p9_virtio_probe - probe for existence of 9P virtio channels
 220  * @vdev: virtio device to probe
 221  *
 222  * This probes for existing virtio channels.  At present only
 223  * a single channel is in use, so in the future more work may need
 224  * to be done here.
 225  *
 226  */
 227
 228 static int p9_virtio_probe(struct virtio_device *vdev)
 229 {
 230         int err;
 231         struct virtio_chan *chan;
 232         int index;
 233
 234         mutex_lock(&virtio_9p_lock);
 235         index = chan_index++;
 236         chan = &channels[index];
 237         mutex_unlock(&virtio_9p_lock);
 238
 239         if (chan_index > MAX_9P_CHAN) {
 240                 printk(KERN_ERR "9p: virtio: Maximum channels exceeded\n");
 241                 BUG();
 242                 err = -ENOMEM;
 243                 goto fail;
 244         }
 245
 246         chan->vdev = vdev;
 247
 248         /* We expect one virtqueue, for requests. */
 249         chan->vq = vdev->config->find_vq(vdev, 0, req_done);
 250         if (IS_ERR(chan->vq)) {
 251                 err = PTR_ERR(chan->vq);
 252                 goto out_free_vq;
 253         }
 254         chan->vq->vdev->priv = chan;
 255         spin_lock_init(&chan->lock);
 256
 257         sg_init_table(chan->sg, VIRTQUEUE_NUM);
 258
 259         chan->inuse = false;
 260         chan->initialized = true;
 261         return 0;
 262
 263 out_free_vq:
 264         vdev->config->del_vq(chan->vq);
 265 fail:
 266         mutex_lock(&virtio_9p_lock);
 267         chan_index--;
 268         mutex_unlock(&virtio_9p_lock);
 269         return err;
 270 }
 271
 272
 273 /**
 274  * p9_virtio_create - allocate a new virtio channel
 275  * @client: client instance invoking this transport
 276  * @devname: string identifying the channel to connect to (unused)
 277  * @args: args passed from sys_mount() for per-transport options (unused)
 278  *
 279  * This sets up a transport channel for 9p communication.  Right now
 280  * we only match the first available channel, but eventually we couldlook up
 281  * alternate channels by matching devname versus a virtio_config entry.
 282  * We use a simple reference count mechanism to ensure that only a single
 283  * mount has a channel open at a time.
 284  *
 285  * Bugs: doesn't allow identification of a specific channel
 286  * to allocate, channels are allocated sequentially. This was
 287  * a pragmatic decision to get things rolling, but ideally some
 288  * way of identifying the channel to attach to would be nice
 289  * if we are going to support multiple channels.
 290  *
 291  */
 292
 293 static int
 294 p9_virtio_create(struct p9_client *client, const char *devname, char *args)
 295 {
 296         struct virtio_chan *chan = channels;
 297         int index = 0;
 298
 299         mutex_lock(&virtio_9p_lock);
 300         while (index < MAX_9P_CHAN) {
 301                 if (chan->initialized && !chan->inuse) {
 302                         chan->inuse = true;
 303                         break;
 304                 } else {
 305                         index++;
 306                         chan = &channels[index];
 307                 }
 308         }
 309         mutex_unlock(&virtio_9p_lock);
 310
 311         if (index >= MAX_9P_CHAN) {
 312                 printk(KERN_ERR "9p: no channels available\n");
 313                 return -ENODEV;
 314         }
 315
 316         client->trans = (void *)chan;
 317         chan->client = client;
 318
 319         return 0;
 320 }
 321
 322 /**
 323  * p9_virtio_remove - clean up resources associated with a virtio device
 324  * @vdev: virtio device to remove
 325  *
 326  */
 327
 328 static void p9_virtio_remove(struct virtio_device *vdev)
 329 {
 330         struct virtio_chan *chan = vdev->priv;
 331
 332         BUG_ON(chan->inuse);
 333
 334         if (chan->initialized) {
 335                 vdev->config->del_vq(chan->vq);
 336                 chan->initialized = false;
 337         }
 338 }
 339
 340 #define VIRTIO_ID_9P 9
 341
 342 static struct virtio_device_id id_table[] = {
 343         { VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
 344         { 0 },
 345 };
 346
 347 /* The standard "struct lguest_driver": */
 348 static struct virtio_driver p9_virtio_drv = {
 349         .driver.name =  KBUILD_MODNAME,
 350         .driver.owner = THIS_MODULE,
 351         .id_table =     id_table,
 352         .probe =        p9_virtio_probe,
 353         .remove =       p9_virtio_remove,
 354 };
 355
 356 static struct p9_trans_module p9_virtio_trans = {
 357         .name = "virtio",
 358         .create = p9_virtio_create,
 359         .close = p9_virtio_close,
 360         .request = p9_virtio_request,
 361         .cancel = p9_virtio_cancel,
 362         .maxsize = PAGE_SIZE*16,
 363         .def = 0,
 364         .owner = THIS_MODULE,
 365 };
 366
 367 /* The standard init function */
 368 static int __init p9_virtio_init(void)
 369 {
 370         int count;
 371
 372         for (count = 0; count < MAX_9P_CHAN; count++)
 373                 channels[count].initialized = false;
 374
 375         v9fs_register_trans(&p9_virtio_trans);
 376         return register_virtio_driver(&p9_virtio_drv);
 377 }
 378
 379 static void __exit p9_virtio_cleanup(void)
 380 {
 381         unregister_virtio_driver(&p9_virtio_drv);
 382         v9fs_unregister_trans(&p9_virtio_trans);
 383 }
 384
 385 module_init(p9_virtio_init);
 386 module_exit(p9_virtio_cleanup);
 387
 388 MODULE_DEVICE_TABLE(virtio, id_table);
 389 MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
 390 MODULE_DESCRIPTION("Virtio 9p Transport");
 391 MODULE_LICENSE("GPL");